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Öğe Investigation of deformation effects on the decay properties of 12C+?Cluster states in 16O(Academic Press Inc., 2018) Soylu A.; Koyuncu F.; Coban A.; Bayrak O.; Freer M.We have analyzed the elastic scattering angular distributions data of the ?+12C reaction over a wide energy range (Elab=28.2 to 35.5 MeV) within the framework of the Optical Model formalism. A double folding (DF) type real potential was used with a phenomenological Woods–Saxon-squared (WS2) type imaginary potential. Good agreement between the calculations and experimental data was obtained. By using the real DF potential we have calculated the properties of the ?-cluster states in 16O by using the Gamow code as well as the ?-decay widths by using the WKB method. We implemented a 12C+? cluster framework for the calculation of the excitation energies and decay widths of 16O as a function of the orientation of the planar 12C nucleus with respect to the ?-particle. These calculations showed strong sensitivity of the widths and excitation energies to the orientation. Branching ratios were also calculated and though less sensitive to the 12C orientation, it was found that 12Cgs+? structure, with the ?-particle orbiting the 12C in its ground state, is dominant. This work demonstrates that deformation, and the orientation, of 12C plays a crucial role in the understanding of the nature of the ?-cluster states in 16O. © 2018 Elsevier Inc.Öğe Investigation of Sub-Coulomb barrier fusion reaction of ? + 4 0 Ca in different models(World Scientific Publishing Co. Pte Ltd, 2017) Koyuncu F.; Soylu A.In this study, microscopic nucleon-nucleon Double Folding (DF) and phenomenological potentials have been used to investigate ? +40Ca reaction observables at sub-barrier energies. In the calculations, semi-classical Wentzel-Kramers-Brillouin (WKB) approach has been used in order to obtain the cross-sections and reaction rates of ? +40Ca. Besides WKB approximation, we have also utilized Talys code in order to get the comparative results and find out the method differences. To estimate the reaction rates, energy-dependent cross-sections and astrophysical S-factors of ?+40Ca have been used. Herewith, differences between models and potentials have been demonstrated using the reaction rate estimates. © 2017 World Scientific Publishing Company.Öğe Screening effects on 12C+12C fusion reaction(Institute of Physics Publishing, 2018) Koyuncu F.; Soylu A.One of the important reactions for nucleosynthesis in the carbon burning phase in high-mass stars is the 12C+12C fusion reaction. In this study, we investigate the influences of the nuclear potentials and screening effect on astrophysically interesting 12C+12C fusion reaction observables at sub-barrier energies by using the microscopic ?-? double folding cluster (DFC) potential and the proximity potential. In order to model the screening effects on the experimental data, a more general exponential cosine screened Coulomb (MGECSC) potential including Debye and quantum plasma cases has been considered in the calculations for the 12C+12C fusion reaction. In the calculations of the reaction observables, the semi-classical Wentzel-Kramers-Brillouin (WKB) approach and coupled channel (CC) formalism have been used. Moreover, in order to investigate how the potentials between 12C nuclei produce molecular cluster states of 24Mg, the normalized resonant energy states of 24Mg cluster bands have been calculated for the DFC potential. By analyzing the results produced from the fusion of 12C+12C, it is found that taking into account the screening effects in terms of MGECSC is important for explaining the 12C+12C fusion data, and the microscopic DFC potential is better than the proximity potential in explaining the experimental data, also considering that clustering is dominant for the structure of the 24Mg nucleus. © 2018 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.
